The role of energy and fluid imbalance in weight changes found during field work in Antarctica.

1. The effect on body-weight of field work in Antarctica when travelling by mechanical transport has been studied. 2. A steady loss of weight (mean 6-2 kg) was found in field, and there was a slow gain on return to less arduous conditions. 3. Changes in skinfold thickness and hip girth suggested that the loss of weight was due to an energy deficit, and the gain was due to an excess of energy. 4. However, although weight was being lost the energy balance was calculated to be positive. This was probably because the expenditure was underestimated as the result of a failure to take into account: (a) the weight and restriction of heavy clothing, (b) the high-protein diet, (c) the difficulty imposed by the terrain, (d) the intensity of the subjects' response to the cold. 5. Daily weight changes were significantly related to climatic conditions. 6. Daily weight changes were significantly related to fluid intakes, but it was not possible to assess with certainty the contribution made by dehydration to the recorded weight loss. 7. Daily fluctuations in weight were greater than those previously found under more standard conditions.